drm/xe/hwmon: Cast result to output precision on left shift of operand

[ Upstream commit a8ad8715472bb8f6a2ea8b4072a28151eb9f4f24 ]

Address potential overflow in result of left shift of a
lower precision (u32) operand before assignment to higher
precision (u64) variable.

v2:
 - Update commit message. (Himal)

Fixes: 4446fcf220ce ("drm/xe/hwmon: Expose power1_max_interval")
Signed-off-by: Karthik Poosa <karthik.poosa@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Cc: Badal Nilawar <badal.nilawar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240405130127.1392426-5-karthik.poosa@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
(cherry picked from commit 883232b47b81108b0252197c747f396ecd51455a)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/xe/xe_hwmon.c b/drivers/gpu/drm/xe/xe_hwmon.c
index 174ed2185481e32d568551e62f1839181a1771d4..a6f43446c779a4b0a2707e3b4562002c87de9100 100644 (file)
--- a/drivers/gpu/drm/xe/xe_hwmon.c
+++ b/drivers/gpu/drm/xe/xe_hwmon.c
@@ -288,7 +288,7 @@ xe_hwmon_power1_max_interval_show(struct device *dev, struct device_attribute *a
         * As y can be < 2, we compute tau4 = (4 | x) << y
         * and then add 2 when doing the final right shift to account for units
         */
-       tau4 = ((1 << x_w) | x) << y;
+       tau4 = (u64)((1 << x_w) | x) << y;
 
        /* val in hwmon interface units (millisec) */
        out = mul_u64_u32_shr(tau4, SF_TIME, hwmon->scl_shift_time + x_w);
@@ -328,7 +328,7 @@ xe_hwmon_power1_max_interval_store(struct device *dev, struct device_attribute *
        r = FIELD_PREP(PKG_MAX_WIN, PKG_MAX_WIN_DEFAULT);
        x = REG_FIELD_GET(PKG_MAX_WIN_X, r);
        y = REG_FIELD_GET(PKG_MAX_WIN_Y, r);
-       tau4 = ((1 << x_w) | x) << y;
+       tau4 = (u64)((1 << x_w) | x) << y;
        max_win = mul_u64_u32_shr(tau4, SF_TIME, hwmon->scl_shift_time + x_w);
 
        if (val > max_win)